An electromagnetic relay superior in insulating characteristic according to the prior art is shown in FIGS. 25 and 26 as an example.
In this electromagnetic relay, a cylindrical frame 1a with one side closed is formed integrally with a base 1 at a generally central portion of the base 1. Into a cavity 1b of the cylindrical frame 1a, an electromagnet block 2 to which a moving core 3 is assembled rockable via a hinge spring 4 is inserted sideways along the axial direction, while fixed contact terminals 5, 6 and a movable contact terminal 7 are inserted and fixed sideways. Then, a pair of elastic arms 8a, 8a provided at one end of a card 8 are engaged with engagement recesses 3a, 3a of the moving core 3, while a pair of projections 8b, 8b provided at the other end of the card 8 are engaged and assembled with engagement recesses 7d, 7d of an elastic contact member 7c forming the movable contact terminal 7. In this way, the card 8 is supported so as to be reciprocatingly movable in parallel to the axial direction of the electromagnet block 2. In addition, reference numeral 9 denotes a casing fittable to the base 1, and the contact terminals 5, 6 and the movable contact terminal 7 have fixed contacts 5b, 6b and a movable contact 7b, respectively, provided at high locations away from their terminal portions 5a, 6a and terminal portion 7a.
When the moving core 3 rocks by its being attracted to or separated from an iron core 2a of the electromagnet block 2 with the electromagnet block 2 energized or de-energized, the card 8 resultantly moves reciprocatingly so that the other end 8c thereof presses and releases the top end portion of the elastic contact member 7c. As a result, the movable contact 7b contacts and separates from the fixed contacts 5b, 6b, alternately, whereby the circuit is opened and closed.
However, the electromagnetic relay according to the prior art has the following three technical problems.
As a first technical problem, according to the prior art electromagnetic relay, the assembly of the card 8 to the movable contact terminal 7 involves a process of forcedly bending the elastic contact member 7c outward. This would cause the elastic contact member 7c to undergo some plastic deformation, which would often incur variations in performance characteristics.
Also, the aforementioned electromagnetic relay involves many assembling operations so that it takes time and labor for the card 8 to be assembled to the elastic contact member 7c, resulting in low productivity.
Further, in the aforementioned electromagnetic relay, not only the drive-use projection 8c presses the elastic contact member 7c, but also a pair of the projections 8b, 8b are engaged with the engagement recesses 7d, 7d of the elastic contact member 7c. Therefore, variations in the assembly precision would make it likely that the drive-use projection 8c makes skew contact with the elastic contact member 7c as the card 8 moves reciprocatingly. This leads to a problem that the movable contact 7b of the movable contact terminal 7 makes non-uniform contact with the fixed contacts 5b, 6b of the fixed contact terminals 5, 6 such that the fixed contacts 5b, 6b are accelerated to wear and shortened in service life.
In the light of the aforementioned first technical problem, a first object of the present invention is to provide an electromagnetic relay which is free from variations in performance characteristics, high in productivity, and long in contact service life.
As a second technical problem, according to the prior art electromagnetic relay, the electromagnet block 2 is inserted sideways along the axial direction into the cavity 1b of the frame 1a provided in the base 1, wherein ahead in the insertion direction, arranged are the fixed contacts 5b, 6b and the movable contact 7b partitioned by the frame 1a. Therefore, whereas the assembly precision of the electromagnet block 2 with respect to the base 1 directly affects the move extent of the card 8, there is a difficulty in assembling the electromagnet block 2 to the base 1 with high precision, such that variations in the performance characteristics often occur.
Also, the base 1 needs to be molded integrally with the frame 1a, and therefore has a complex configuration. This makes the molding process difficult as well as the manufacture of the mold also difficult.
Further, the electromagnet block 2 needs to be inserted into the base 1 sideways along the axial direction, a direction other than that in which the other components are assembled. As a result, the automatic assembling machines become complex to arrange in the assembly line, which leads to a problem that the automatization of assembly processes demands more tasks.
In the light of the aforementioned second technical problem, a second object of the present invention is to provide an electromagnetic relay which is free from variations in performance characteristics, and which allows easy accomplishment of required molding work, manufacture of molds, and automatization of assembly.
As a third technical problem, according to the prior art electromagnetic relay, since the fixed contacts 5b, 6b and the movable contact 7b are located at high positions away from the top surface of the base 1, the fixed contacts 5b, 6b and the movable contact 7b may result in large deflections even when the fixed contact terminals 5, 6 and the movable contact terminal 7 are slightly inclined by thermal deformation of the base 1 due to elevated outside temperature. Therefore, the performance characteristics tend to vary due to shifts of the fixed contacts 5b, 6b and the movable contact 7b relative to each other.
Further, since the elastic contact member 7c has only a short effective length, the elastic contact member 7c needs to be reduced in thickness in order to ensure a specified spring constant. Therefore, the elastic contact member 7c tends to deform during the process of caulking or other fixing work, which leads to a problem of troublesome assembly work.
In the light of the aforementioned third technical problem, a third object of the present invention is to provide an electromagnetic relay which will not vary in performance characteristics even with varying outside temperature, and which is easy to assemble.